Manufacture of cellulose ester products



Patented Mar. 13, 1934 DIANUFACTURE OF CELLULOSE ESTER PRODUCTS HenryDreyfus, London, England 4 Claims.

acetates or cellulose esters of higher homologues of acetic acid, forexample, of propionic acid or butyric acid.

The said application describes the production of the esters which formthe starting materials of the present invention from a variety ofcellulosic materials including cotton and other forms of cellulose andnear conversion products of cellulose, and also from already esterifiedor etherified cellulose.

from

The cellulosic materials are preferably pretreated prior toesterification so as to enhance their reactivity. This pretreatment mayin the case of certain materials, for example wood pulps, comprise aninitial alkaline purifying treatment followed by a pretreatment withformic acid or other suitable acid. In the case of other and purermaterials, for example cotton, gmetreatment may involve merelysubjection of the materials to the action of formic acid or otherorganic acid under various conditions. The materials whether or not theyhave been pretreated are esterified, in solution or in suspension, inthe presence of a stannic halide, e. g. stannic ride or bromide.

chlo- There may be present during esterification other halides, e. g.halides of iron, cobalt, nickel, manganese or copper, hydrochalideacids, e. g. hydrochloric acid, other esterification catalysts, andsuitable diluents, e. g. benzene or solvents for the cellulose esters,e. g. acetic acid. In order to avoid degradation of the cellulosemolecule the acetylation or other esterification is preferably carriedout at temperatures not exceeding 50 C. The most valuable esters areobtained if the esterificaticn is performed at low temperatures, forexample below atmospheric e. g. 10 C. to 5 or 0 C. or lower, at ordinarytemperatures or at temperatures, such as 20 to 30 C.

not substantially above atmospheric.

have new and highly desirable properties.

For

example when they are subjected to ripening treatments it is found thatthey reach acetonesolubility with practically complete elimination ofthe catalysts when they still have an unusually high acidyl content, forexample, on the order of 69 56% and higher calculated as acetic acid,and that filaments or other products spun from the acetates or otheresters so produced are highly resistant to the delustering action ofmoist steam or other hot or boiling aqueous media.

These and other properties of the new cellulose acetates or other estersrender them very valuable indeed for the production of artificial silksand the like, films, celluloid substitutes or other thermoplasticmasses, moulding powders 70 or moulded articles, etc. The presentapplication has for its object the manufacture of in-' dustrial productsfrom the said acetates or other esters.

The cellulose acetates or other cellulose esters resulting from theacetylation or other esterification may be used in their esterificationsolution or in solutions of the primary esterification products, or theymay be subjected to secondary treatments or reactions as is described inthe said application for the purpose of changing their solubilities. Animportant advantage of the present invention is the fact that thecellulose acetates or other esters can be so employed in their primaryesterification solutions in their difierent stages or phases ofacetylation or esterification.

Example I 100 parts of cotton cellulose are pretreated with formic acid,for example by treatment with 500 to 1000 parts or more of formic acidof about 85%-100% strength, allowing to stand for some hours in the coldand hydro-extracting or by impregnating with about 15 parts of formicacid of 75-85% strength and then allowing to stand for about 8-12 hoursat ordinary temperature. If desired the material may then be washed withwater, benzol or the like to remove the formic acid and centrifuged ordried. The parts of 100 pretreated material are introduced in theacetylator into a mixture of 600 parts of acetic anhydride, 600 parts ofacetic acid, 10 parts of stannic chloride and 10 parts of hydrochloricacid, (calculated as HCl) either in the form of the fuming aqueoussolution (35% strength) or in solution in the acetic acid, and the massis constantly mixed or stirred during the reaction, which is conductedat about ordinary atmospheric temperature. The acetylation proceedssmoothly and a clear solution is obtained. The solution may either beused directly or the cellulose acetate may be precipitated andredissolved or worked up in any desired manner.

Example II 100 parts of cotton cellulose pretreated as in Example I areintroduced in the acetylator into a mixture of 800 parts of acetic acid,300 parts of-- acetic anhydride and 20 parts of stannic chloride. Thereaction is carried out in the cold with constant mixing or stirring. Aclear solution is obtained of a cellulose acetate of very highviscosity.

Example III of acetic anhydride are introduced. The reaction isconducted at about 20 0-40 0. with constant mixing or stirring of themass.

Example IV 100 parts of cotton cellulose are introduced in theacetylator into a mixture of 800-1000 parts of acetic acid, 400 parts ofacetic anhydride, 10 parts of stannic chloride, 10 parts of ferricchloride and 10 parts of hydrochloric acid (calculated as H01) either inthe form of aqueous solution (e. g. 35%) or in solution in the aceticacid, the reaction being then conducted in the cold With constantstirring or mixing. A solution is obtained of a cellulose acetate ofhigh viscosity.

In a similar manner stannic bromide or stannic iodide may be used withor without halides or" iron, cobalt, nickel, manganese or copper toeffect the acetylation and furthermore by employing the appropriateanhydride or anhydrides other cellulose esters or mixed esters may beobtained. It is found that as compared with prior processes, the use ofstannic halides as catalysts much facilitates the production ofcellulose esters of higher fatty acids, e. g. propionic acid.

Further, the new cellulose esters of high quality may be dissolved insuitable solvents, for example acetone, ethyl alcohol-acetone, methylalcohol-acetone, or the very low boiling solvents, for instance methylformate, acetaldehyde and formaldehyde, or in mixtures of such solvents.Also suitable high boiling solvents or plasticising or softening agentscan be readily incorporated with them or their solutions in volatilesolvents and/or very low boiling solvents. For either wet ordry-spinning processes the esters may be employed in the form ofsolutions of relatively low concentration for instance 5-8% or of mediumconcentration for example 10-20%, or of high concentration containingover 20%, e. g. 25-30% or more.

The artificial silks and the like produced from the new secondary estersof high ester content are found to be much more resistant to delustringby hot or boiling aqueous liquids or moist steam than the celluloseester products produced hitherto, and they may even resist delustringaltogether.

As examples of suitable precipitating liquids for use in wet-spinningprocesses the following may be mentioned:-alcohols, for example methyland ethyl alcohols and their homologues; coal tar, petroleum or otherhydrocarbons, for instance benzene, toluene and their homologues,gasoline, kerosene and the like; and aqueous liquids containing, forexample, suitable proportions of mineral acids, e. g. sulphuric acids,of acid salts, e. g. bisulphates, of neutral salts, e. g. sodium,potassium, calcium or magnesium chloride, or, as described in priorBritish specifications Nos. 177,868 and 179,234, of thiocyanates, zincchloride, acetone, diacetone alcohol, alcohol, acetic acid, formic acidor other salts or substances having a latent solvent power for thecellulose acetate or other ester. Furthermore, such precipitatingliquids may, if desired, be incorporated in suitable proportions in thespinning solutions prior to extrusion.

For the production of artifical silks or fibres, films, etc. as well asfor the production of thermoplastic masses, articles and the like,plasticizing or softening agents or high boiling solvents may beincorporated in the esters or in their solutions.

What I claim and desire to secure by Letters Patent is:

1. Articles having no substantial thickness comprising acetone-solublecellulose acetate having an ester content, calculated as acetic acid, ofat least 56% and which are inherently substantially resistant to thedelustering action of hot aqueous media.

2. Artificial silk comprising acetone-soluble cellulose acetate whichhas an ester content calculated as acetic acid of at least 56 and whichis inherently substantially resistant to the delustering action of hotaqueous media.

3. Dry-spun artificial silk comprisingacetonesoluble cellulose acetatewhich has an ester content calculated as acetic acid of at least 56% andwhich is inherently substantially resistant to the delustering action ofhot aqueous media.

4. Films comprising acetone-soluble cellulose acetate which has an estercontent calculated as acetic acid of at least 56% and .which areinherently substantially resistant to the delustering action of hotaqueous media.

HENRY DREYFUS.

